Editing Tornado code (section)

In [[coding theory]], '''Tornado codes''' are a class of [[erasure code]]s that support [[error correction]].  Tornado codes require a constant C more redundant blocks than the more data-efficient [[Reed–Solomon erasure code]]s, but are much faster to generate and can fix erasures faster.  Software-based implementations of tornado codes are about 100 times faster on small lengths and about 10,000 times faster on larger lengths than Reed–Solomon erasure codes.{{sfn|Byers|Luby|Mitzenmacher|Rege|1998}} Since the introduction of Tornado codes, many other similar erasure codes have emerged, most notably [[Online codes]], [[LT codes]] and [[Raptor codes]].

Tornado codes use a layered approach.  All layers except the last use an [[Low-density parity-check code|LDPC]] error correction code, which is fast but has a chance of failure.  The final layer uses a Reed–Solomon correction code, which is slower but is optimal in terms of failure recovery.  Tornado codes dictates how many levels, how many recovery blocks in each level, and the distribution used to generate blocks for the non-final layers.